Ultrafast lasers, such as picosecond or femtosecond lasers, with pulse energy in micro joule (μJ) level are very desirable for many scientific studies and industrial applications. It is well known that the ultrafast laser can provide nano-scale dimension ablation without the detrimental thermal effect, facilitating the so called “cold” processes. This high peak power μJ pulse can also create a very strong electromagnetic field near the vicinity of the materials being machined, which offers an opportunity to practically verify many theoretical predictions of high electromagnetic field physics.
A high power fiber laser may comprise a fiber laser oscillator and multiple stages of fiber laser amplifiers. The fiber laser oscillator sets the laser's wavelength, pulse width, and repetition rate, while the fiber laser amplifiers boost the laser power to a required level. The fiber laser may optionally include a free space solid state power amplifier for a last stage power amplifying.
State of the art ultrafast lasers used in industrial applications are complex and expensive. The development focus in the commercial fiber laser industry is aimed at increasing the output power while reduced its manufacturing cost, i.e., to improve the current performance-over-cost ratio. Accordingly, less expensive high power ultrafast lasers are demanded.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention.